A SIP includes a number of integrated circuits (ICs) enclosed in a single package or module. The SIP performs all or most of the functions of an electronic system, and is commonly used inside products including mobile phones, personal digital assistants (PDAs) and digital music players. In a SIP, individual ICs can be stacked vertically (3D arrangements) or arranged horizontally. ICs can be internally connected by fine wires that are bonded to the package. Alternatively, with a flip-chip technology, solder bumps are used to join stacked chips together.
Some SIPS comprise die that include through silicon vias or more generally through substrate vias (referred to herein as “TSV die”), such as a logic/processor die, where the TSVs are arranged in one or more TSV arrays that provide vertical connections through the full thickness of the TSV die. TSVs allow vertical stacking of multiple die, and interconnecting them without using conventional wire bonding or flip-chip bumping. For example, TSVs can be used for stacking up a series of memory chips and can provide a signal path or heat transfer path between the die.
Some TSVs include protruding TSV tips that protrude from the bottomside (non-active side) of the TSV die. Such TSV die are often thin, such as 30 μm to 80 μm in thickness. Thin TSV die are prone to warpage which can result in unreliable connections to the TSVs. For a consistent and reliable connection, flatness of such TSV die should generally be kept within a few μms over the full area of the TSV die.
In one process for forming SIPs including thin TSV die, thin TSV die can be bonded to another die for mechanical support before bonding the TSV die attached to the other die to a substrate. For example, a singulated TSV die may be attached to a memory die (or module) using a flat carrier, followed by the TSV die/memory die being attached to a substrate, such as an organic substrate. In another SIP formation process, a TSV die is bonded to a substrate, followed bonding a top die to the TSV die. In either case, the substrate can include a ball grid array (BGA), and the SIP may be attached to a printed circuit board (PCB).
There are several disadvantages to these known SIP processes. It is not possible to test the TSV die before attaching the top die (e.g., memory die). Therefore, failure of the TSV die or connections from the TSV die to the substrate can cause yield loss including the scrap of good to die (e.g., memory die). The end-user may also demand different memory density for their system (4 Gb, 8 Gb 16 Gb, etc.), creating a need to develop multiple SIP products. SIP vendors have to also purchase memory and keep memory devices in inventory.
Another problem for stacked die SIPs is heating due to power dissipation during operation. Recently, as computing performance has increased, power consumption of the TSV die has increased. Individual ICs in the SIP, such as a memory die on top of the TSV die, may become overheated if cooling is not properly and adequately provided. The space between individual ICs in the die stack may also be too small for providing cooling channels because the gaps are generally too small for fluid flow. A heat spreader can be attached on top of the top die (e.g., memory die) in a stacked SIP, but this is not an efficient cooling arrangement since the thermal resistance of the top die prevents efficient power dissipation from the TSV die, and heating of the top die (e.g., memory die) causes higher power consumption for the SIP system.